Absorbent dryer



Jan. 10 1967 KRlKORlAN 3,296,71Q

ABSORBENT DRYER Filed July 15, 1965 2 Sheets-Sheet ,l.

2 Sheets-Sheet 2 G. KRIKORIAN ABSORBENT DRYER Jan. 10, 1967 Filed July 15, 1965 United States Patent 3,296,710 ABSORBENT DRYER Caro Krikorian, i'axton, Mass, assignor to Rice Barton Corporation, Worcester, Mass, a corporation of Massachusetts Filed July 15, 1965, Ser. No. 475,315 4 Claims. (Cl. 34-95) The present invention relates to an improved absorbent dryer for removing liquid from a travelling web, and is a continuation-in-part of my co-pending application Serial No. 270,946. filed April 5, 1963, now abandoned for Absorbent Dryer. The invention relates more particularly to improved absorbent dryer of the general type in which moisture is transferred from the web to a layer of absorbent porous material having an internal structure of sufficient hardness to prevent closing of said pores under the pressure of the press nip.

While the high absorptive capacity of such materials has long been recognized, difficulties have been encountered in providing a de-watering device of this descrip tion in which moisture picked up by the absorptive layer will be so entrapped therein as to prevent any return of moisture to the travelling Web by suction as the surfaces separate upon leaving the nip, in combination with means for thereafter very rapidly driving out such moisture as the absorbent layer travelling in a closed path returns to the nip.

Principal objects of the invention are to provide a novel apparatus and method for de-watering a travelling web, wherein the liquid is transferred at a press nip to the non-collapsible pores of a hard, porous, absorbent layer travelling in a closed path. but without any tendency of the water to reenter the web as the pressure at the nip is released, and is thereafter rapidly and efficiently driven off, in a continuous operation well adapted for de-Watering webs travelling at high speeds.

It is a further object to provide a web de-w-atering device well adapted for removing liquid from a travelling web of low moisture content with such efficiency as to still further reduce the moisture level to a level lower than heretofore previously considered practicable.

More specifically, it is an object of the invention to provide an improved apparatus of the general type re ferred to for de-watering a travelling web, in which a thin layer of microporous material is employed, so that liquid forced into the microporous layer at the nip is entrapped by the surafec tension created within the micropores, and from which the moisture is thereafter driven off as a vapor by the application of heat over the surface area of said microporous layer.

With these and other objects in view as may hereinafter appear, the several features of the invention will be apparent to one skilled in the art from the following description taken in connection with the accompnaying drawings in which:

FIG. 1 is a view in side elevation of a drum dryer embodying the several features of the invention;

FIG. 2 is a detail sectional view taken on a line 22 of FIG. 1 showing the relation of the porous surface coated drum, press roll and water hood;

FIG. 3 is a detail sectional view similar to FIG. 2, but disclosing an alternative construction illustrating two opposed drying drums each having a working surface composed of a porous absorbent material; and

FIGS. 4 and 5 illustrate a modification of the invention in which the de-watering device comprises an endless belt externally heated by hot air;

FIG. 4 being an end view of the device with the hood broken away to show underlying parts; and

FIG. 5 being a sectional view taken on a line 55 of FIG. 4.

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The rotary drum dryer illustrated in FIGS. 1 and 2 of the inst-ant application comprises a rotary drying drum which has a layer of porous absorbent material having sufficient hardness so that the pressure applied thereto in the press nip will not collapse the pores of the nip. The drum consists of a hollow cylinder of steel or cast iron, and has adhered thereto a coating of powdered aluminum oxide, preferably $4 to A1" in thickness, which provides the porous absorbent layer referred to. This material is highly absorptive and the pores, being of micron size, produce a degree of surface tension or capillarity which tends to entrap or lock in any moisture absorbed thereby.

A travelling web 8 to be dried is brought into intimate contact With the porous absorbent surface of the drum by means of a press nip provided by a cooperating press roll which may, for example, be a rubber-covered steel cylinder. Water contained in the web is thus transferred or pressed into the pores of the hard surface absorbent layer. This transfer of the water to the porous surface of the drum is extremely rapid. The water thus transferred to the micropores of the absorptive layer is now locked in by the surface tension and capillary forces referred to, and is thus prevented from flowing in the reverse direction back into the web as the surfaces separate following the mp.

In accordance with the invention, the water taken up by the hard absorbent material is now vaporized and driven off from the open micropores or capillaries of the absorbent layer with a rapidity and efliciency which makes possible a very high linear rate of travel of the web over the drying drum.

In the preferred embodiment of the invention shown,

the water taken up by the pores of the porous absorbent layer is vaporized and driven off from the drum at a rate commensurate with the high speed rotation thereof in the following manner:

The drum is internally heated by a heating medium which may, for example, be steam causing heat to be transferred to said porous absorbent layer including the very large internal surface area of the pores so that the water adhering thereto is almost instantly vaporized. It will be understood that suificient heat may be applied to effect such rapid vaporization of the entrapped water without injury to the travelling web which is protected by the insulating coating of water which is transferred to the drum and by the very short period of time in which the web is engaged with the drum at the press nip. The water expressed from the web at the nip is pressed very rapidly into the micropores of the :heated drum, is sufficiently locked in or entrapped by the surface tension which tends to be set up within pores of micron size to prevent any reverse flow of the liquid back into the web as a result of mechanical forces set up which would include suction, osmosis or centrifugal pull as the surfaces separate upon leaving the nip, and is then driven off from the pores with great rapidity during the travel of the absorbent layer in a closed path back to the nip by the application of heat simultaneously and uniformly to all portions of said absorbent layer of sufficient intensity to produce an almost instant vaporization of the entrapped moisture.

A further feature of the invention consists in the provision of an air hood Within which all portions of the drying drum except for that part of the surface passing through the nip are encased. A drying medium as, for example, hot air is introduced into the hood in order to facilitate the vaporization of water from the absorbent layer of the drum, and an exhaust outlet is provided from the hood to carry off the vapor driven off from the surface of the drum. The hood employed, as above described, has the effect of lowering the temperature at which the water contained in the pores will be vaporized. Since vaporization is a function of the difference between the inside stream and the outside vaporization temperature, it will be appreciated that the increased differential achieved by the use of the hood has the effect of substantially increasing the drying rate of the drum.

Referring more specifically to the drawings, FIGS. 1 and 2, the drum dryer illustrated comprises a drying drum which may, for example, be in the form of a steel or cast iron shell 12, and the circumferential surface of which comprises a layer of a porous absorbent material 14 of sufficient strength to prevent crushing or closing of the pores under the rolling pressure applied thereto. Requisites of the porous material 14 include suitable qualities of wettability, hardness, void volume and capillarity to absorb, contain, and retain the liquid transferred thereto at the press nip.

Qualities which tend to overcome the surface tension faces which resist absorption will include the micro scopically rough surface, cleanliness of the surface, and a small percentage of moisture. While in the illustrated example a bone hard ceramic material is described it will be understood that other materials such as porous hard rubber, porous plastics, porous Teflon or porous nylon having micropores and a sufficient degree of hardness to prevent collapse of the pores at the press nip could be employed. The thickness of the absorbent layer and degree of porosity affect the void volume required to contain the liquid expressed from the travelling web at the nip. A layer of powdered aluminum oxide varying from A to /4 may be required depending upon the moisture content and thickness of the web. The size of the micropores is of great importance, to provide the required capillarity or surface tension to retain the moisture in the pores of the porous layer when leaving the nip. A pore size ranging between 10 and microns may be regarded as acceptable.

I have made the further discovery that a layer of liquid saturated microporous material of the type herein described adhered to a liquid impervious metal drum or band, which effectively holds its liquid content against such mechanical forces as air suction, air pressure, centrifugally applied pressure and the like, may be de-watered with great rapidity when heat in sufficient amounts to cause vaporization is applied uniformly and continuously over the entire area of said layer. Heat may be applied internally against the drum or band, or may be applied externally by any suitable heating means which will include steam, heated air, electrical heating units and the like. The vapor produced is collected preferably in a hood, and is drawn off by any suitable means. As hereinafter noted the efficiency of the de-watering operation may be further increased by introducing a drying medium into the hood, and by the use of a vacuum type exhaust outlet from the hood.

The shell 12 is formed at each end with headers 16 and 18 which are secured to a rotatable tubular drum support shaft 20. The drum supporting shaft 20 is rotatably supported in bearings formed on two bearing supports 24 and 26. The drum 10 may be driven from any suitable source, for example, the electric motor 28 and the meshing gears 30 and 32 mounted respectively on the armature shaft 34 of the motor and on the supporting shaft 20.

The drum assembly includes also a press roll 38 which may have a rubber cover 39 and has formed at each end thereof trunnions which are supported in bearings formed respectively in the bearing supports 24 and 26. The bearing supports referred to are adjustable in a wellknown manner (not shown) to control the spacing and pressure applied by the roller 38 in the nip to maintain an intimate contact between the web and the porous covering 14 of the drum. The roller 38 is suitably driven by means of an electric motor 40 and meshing gears 42 and 43 secured respectively to the aramature shaft of the motor 40 and to one of the trunnions for the roller 38.

The continuous rolling press action and the intimate Contact between the web and porous covering 14 produced by the press roller 38 at the press nip have the effect of squeezing water continuously from the sheet into the pores of the porous surface layer 14 of the drum.

In order to effect a rapid evaporation of moisture from the porous surface of the drum, the drum is internally heated by the introduction therein of a heating medium such as steam, hot oil, hot gases, or hot water through supply connections which may include an inlet junction 54 connected with one end of the tubular support shaft 20 and a plurality of perforations or outlets from the shaft 20 into the drum. Any condensate which may form in the drum is drawn off through one or more siphons 60 connected by pipes 62 and a manifold 64 mounted within the tubular drum supporting shaft 20 to an outlet junction 66 at the end of shaft 28. With the arrangement described, the drum including the layer of non-collapsible porous absorbent material 14 and contained moisture is heated to a point at which a rapid vaporization of water coming in contact with the very large surface area of the pores takes place.

The vaporization of water is continuous over the entire porous absorbent material covered surface of the drum.

Further in accordance with the invention, the entire external surface of the drum, with the exception of that portion passing through the press nip, is enclosed within a hood 70, which is formed with a narrow slot opening 72 to permit the emergence of said web engaging portion of the drum surface. The hood 70 is secured firmly in position by means of brackets 74. The interior of the hood is conditioned to assist to a maximum extent the vaporizing process by the injection of a drying medium as, for example, hot air into the hood through a supply inlet 76. The vapor continuously produced during the operation of the dryer is collected in the hood, and is then removed from the hood through a vapor exhaust outlet 78.

A modified form of the invention is shown in the somewhat diagrammatic FIG. 3 in which there is provided a second drying drum 84 having a circumferential surface which comprises a thin layer of porous absorbent material 86. The drying drum 84 is completely enclosed in a water vapor removing hood 88 which is formed with a slot 90 of sufiicient width to permit the emergence of a small portion of the surface of the drum 84 which engages the travelling web at the location of the nip. The drum 84 is steam heated in the same manner as the drum 10 and the hood 88 is similarly provided with a hot air inlet and a vapor exhaust outlet. Inasmuch as the drum 84, together with its heating connections, and the hood 88, together with the inlet and outlet connections referred to, are in all respects similar to the corresponding elements of the lower drum assembly previously described, no further illustration or description of these parts is believed necessary.

The modified form of the invention shown in FIG. 3 has the advantage that water can be simultaneously transferrcd to absorbent drying drums at opposite sides of webs which are so constructed or are of such thickness that all of the water cannot be pressed readily through the web to a drum at one side thereof.

FIGS. 4 and 5 of the drawings illustrate a further modification of the invention in which the absorbent element comprises a belt or band travelling in a closed path having adhered thereto a layer of absorbent material with micropores which will accept and hold liquid transferred thereto at a press nip, and from which the liquid can be, thereafter, rapidly expelled by the application of heat sufiicient to cause vaporization over the area of said microporous layer. An absorbent element in the form of a flexible band having the required characteristics is provided by a steel band or tape 102 which is preferably about .045

inch in thickness to which is adhered a layer of powdered aluminum oxide 104 which may be about .030 inch in thickness to provide an endless band which is sufficiently flexible to travel in a closed path on the supporting rollers shown.

In the embodiment of FIGS. 4 and 5 a press nip is provided between a rubber covered roll 106 and the band 100 supported on a press roll 108 for a paper web 110 travelling from left to right. The band 100' is arranged to pass around a take-up roll 112 and a guide roll 114 back to the nip. Heat is supplied in sufficient quantities to effect a very rapid vaporization of the liquid pressed into the microporous layer 104 at the nip by means of three hot air units 116, 118, and 120 overlying the runs between roll 108 and 112, rolls 112 and 114, and rolls 114 and 108. Each said hot air unit is provided with a hot air inlet 122 and a series of transverse slots 124-thro11gh which hot air is directed against the surface of the rapidly travelling microporous absorptive layer of the band 100*. The rubber covered roll 106 and the band 100 supported on rolls 108, 112 and 114 are continuously driven at the same linear speed as the paper web 110 by suitable driving connections which may be similar to the drive shown for the dryer illustrated in FIGS. 1 and 2 and is therefore not specifically illustrated.

In order to further improve the efficiency of the dewatering operation, the absorbent element of the dryer consisting of the band 100 together with the hot air units 116, 118 and 120 are encased in a hood 126 which is formed with a narrow slot 128 to permit the emergence of the travelling band 100 at the nip, and an outlet 130 through which accumulated vapor and condensed liquid are drawn off.

The invention having been described what is claimed is:

1. An absorbent dryer having, in combination, a rotary drying drum and press roll supported in press nip producing relation, said rotary drum having an external layer of a porous absorbent material of sufficient hardness to prevent closing of said pores under the pressure of said press nip, steam heating means extending within the drum for uniformly heating the drum surface including said external absorbent layer to a sufficient degree to effect rapid vaporization of liquid from said pores, a vapor collecting hood substantially enclosing the absorbent layer covered surface of said drum, means for introducing a drying medium into said hood, and means for exhausting the vapors collected in said hood.

2. An absorbent dryer having, in combination, a rotary drying drum and a press roll supported in a press nip producing relation, said rotary drying drum having an external layer of a porous absorbent material of sufficient hardness to prevent closing of said pores under the pressure of said press nip, means located within the drum for continuously and uniformly heating the drum sunface including said external absorbent layer, a vapor collecting hood substantially enclosing the absorbent layer covered surface of said drum, said hood having a narrow slot opening to permit the emergence of that portion of the surface of the rotating drum at said press nip, and means for exhausting the vapor collected in said hood.

3. An absorbent dryer having, in combination, a pair of rotary drying drums supported in a press nip producing relation, each said rotary drying drum having an external layer of a porous absorbent material of sufficient hardness to prevent closing of said pores under the pressure of said press nip, means for introducing a heating medium into each drum for continuously and uniformly heating the drum surfaces including each said external absorbent layer, a vapor collecting hood associated with each said drum substantially enclosing the absorbent layer covered surface of the respective drum, each said hood having a narrow slot opening to permit the emergence of that portion of the surface of the drum at the press nip, means for introducing a heating medium into each said hood, and means for exhausting the vapor collected in each said hood.

4. An absorbent dryer for removing liquid from a travelling web having, in combination, a press nip assembly including travelling web engaging surfaces, and means including a rotating roll relatively moving said travelling press surfaces together in a press nip pattern, said press surfaces including an endless flexible steel band having a thickness in the order of .045 inch, a layer of microporous powdered aluminum oxide adhered to said band having a thickness in the order of .030 inch, said micropores being of such size to accept a flow of said liquid into said layer and to create capillary force therein to entrap said liquid against an out flow from said pores in leaving the nip, supporting means for said band including a nip positioning roll, a guide roll, and a take-up roll, and means for applying heat continuously and uniformly over the area of said layer of powdered aluminum oxide while travelling in an endless path to and from said nip to cause rapid vaporization of said entrapped liquid from the pores of said layer.

References Cited by the Examiner UNITED STATES PATENTS 1,571,214 2/1926 Powers 34-71 1,759,600 5/1930 Wilshire 34-9 X 1,990,102 2/1935 Smith 16:2372 2,185,766 1/1940 Higby 34-95 X 2,209,759 7/1940 Berry 349 X 2,436,028 2/ 1948 Wiegerink 34-9 3,110,612 11/1963 Gottwald et al. 34-111 X FOREIGN PATENTS 438,475 11/1935 Great Britain.

FREDERICK L. MATTESON, JR., Primary Examiner.

WILLIAM F. ODEA, Examiner.

D. A. TAMBURRO, Assistant Examiner. 

1. AN ABSORBENT DRYER HAVING, IN COMBINATION, A ROTARY DRYING DRUM AND PRESS ROLL SUPPORTED IN PRESS NIP PRODUCING RELATION, SAID ROTARY DRUM HAVING AN EXTERNAL LAYER OF A POROUS ABSORBENT MATERIAL OF SUFFICIENT HARDNESS TO PREVENT CLOSING OF SAID PORES UNDER THE PRESSURE OF SAID PRESS NIP, STEAM HEATING MEANS EXTENDING WITHIN THE DRUM FOR UNIFORMLY HEATING THE DRUM SURFACE INCLUDING SAID EXTERNAL ABSORBENT LAYER TO A SUFFICIENT DEGREE TO EFFECT 